The Synthesis and Anion Recognition Property of Symmetrical Chemosensors Involving Thiourea Groups: Theory and Experiments

The synthesis of four symmetrical compounds containing urea/thiourea and anthracene/nitrobenzene groups was optimized. N,N'-Di((anthracen-9-yl)-methylene) thio-carbonohydrazide showed sensitive and selective binding ability for acetate ion among the studied anions. The presence of other competitive anions including F(-), H₂PO₄(-), Cl(-), Br(-) and I(-) did not interfere with the strong binding ability. The mechanism of the host-guest interaction was through multiple hydrogen bonds due to the conformational complementarity and higher basicity. A theoretical investigation explained that intra-molecular hydrogen bonds existed in the compound which could strengthen the anion binding ability. In addition, molecular frontier orbitals in molecular interplay were introduced in order to explain the red-shift phenomenon in the host-guest interaction process. Compounds based on thiourea and anthracene derivatives can thus be used as a chemosensor for detecting acetate ion in environmental and pharmaceutical samples.